Erectile dysfunction (impotence) is the inability to achieve or maintain an erection sufficiently rigid for sexual intercourse. Sexual drive and the ability to have an orgasm are not necessarily affected. Because all men have erection problems from time to time, doctors consider erectile dysfunction to be present if attempts at intercourse fail at least 25% of the time.

Erectile dysfunction is not new in either medicine or human experience, but it is not easily or openly discussed. Cultural expectations of male sexuality inhibit many men from seeking help for a disorder that can usually benefit from medical treatment.

The Penis and Erectile Function

The Structure of the Penis. The penis is composed of the following structures:

• Two parallel columns of spongy tissue called the corpus cavernosa, or erectile bodies.
• A central spongy chamber called the corpus spongiosum, which contains the urethra, the tube that carries urine from the bladder through the penis.

These structures are made up of erectile tissue. Erectile tissue is rich in tiny pools of blood vessels called cavernous sinuses. Each of these vessels are surrounded by smooth muscles and supported by elastic fibrous tissue composed of a protein called collagen.

Erectile Function and Nitric Oxide. The penis is either flaccid or erect depending on the state of arousal. In the flaccid, or unerect, penis, the following normally occurs:

• Small arteries leading to the cavernous sinuses contract, reducing the inflow of blood.
• The smooth muscles regulating the many tiny blood vessels also stay contracted, limiting the amount of blood that can collect in the penis.

During arousal the following occurs:

• The man's central nervous system stimulates the release of a number of chemicals, including nitric oxide, which is now considered the main contributor for eliciting and maintaining erection.
• Nitric oxide stimulates production of cyclic GMP, a chemical that relaxes the smooth muscles in the penis. This allows blood to flow into the tiny pool-like cavernous sinuses, flooding the penis.
• This increased blood flow nearly doubles the diameter of the spongy chambers.
• The veins surrounding the chambers are squeezed almost completely shut by this pressure.
• The veins are unable to drain blood out of the penis and so the penis becomes rigid and erect.
• After ejaculation or climax, cyclic GMP is broken down by an enzyme called phosphodiesterase-5 (PDE5), causing the penis to become flaccid (unerect) again.

Important Substances for Erectile Health

A proper balance of certain chemicals, gases, and other substances is critical for erectile health.

Collagen. The protein collagen is the major component in structural tissue in the body, including in the penis. Excessive amounts, however, form scar tissue, which can impair erectile function.

Oxygen. Oxygen-rich blood is one of the most important components for erectile health. Oxygen levels vary widely from reduced levels in the flaccid state to very high in the erect state. During sleep, a man can normally have three to five erections per night, bringing oxygen-rich blood to the penis.

Testosterone and Other Hormones. Normal levels of hormones, especially testosterone, are essential for erectile function, though their exact role is not clear.

Erectile Dysfunction and Oxygen Deprivation

The primary cause of oxygen deprivation is ischemia -- the blockage of blood vessels. The same blood flow-reducing conditions that lead to heart disease, such as atherosclerosis, may also contribute to erectile dysfunction. Conditions such as unhealthy cholesterol levels, diabetes, and high blood pressure are associated with atherosclerosis and heart disease.

In-Depth From A.D.A.M. Risk Factors

More than 18 million American men over age 20 have erectile dysfunction, and about 600,000 men age 40 - 70 experience erectile dysfunction to some degree each year.

Age

For most men, erectile dysfunction is primarily associated with older age. While ED affects less than 10% of men in their 20s, and 5 - 17% of men in their 40s, about 15 - 34% of men in their 70s have ED.

Nevertheless, impotence is not inevitable with age. In a survey of men over 60 years old, 61% reported being sexually active, and nearly half derived as much if not more emotional benefit from their sex lives as they did in their 40s.

Severe erectile dysfunction often has more to do with disease than age itself. In particular, older men are more likely to have heart disease, diabetes, and high blood pressure than younger men. Such conditions and some of their treatments are causes of erectile dysfunction.

Lifestyle Factors

Smoking. Smoking contributes to the development of impotence, mainly because it increases the effects of other blood vessel disorders, including high blood pressure and atherosclerosis.

Alcohol Use. Heavy drinking can cause erectile dysfunction. Alcohol depresses the central nervous system and impairs sexual function.

Drug Abuse. Illicit drugs such as heroin, cocaine, methamphetamines, and marijuana can affect sexual function.

Lack of Exercise. A sedentary lifestyle can lead to obesity and other health problems associated with erectile dysfunction.

In-Depth From A.D.A.M. Causes

Over the past decades, the medical perspective on the causes of erectile dysfunction has shifted. Common wisdom used to attribute almost all cases of impotence to psychological factors. Now doctors believe that up to 85% of impotence cases are caused by medical or physical problems. Only 15% are completely psychologically based. Sometimes, erectile dysfunction is due to a combination of physical and psychological causes.

A number of medical conditions share a common problem with erectile dysfunction -- the impaired ability of blood vessels to open and allow normal blood flow.

Heart Disease, Atherosclerosis, and High Blood Pressure

Heart disease, atherosclerosis, high blood pressure and high cholesterol levels are major risk factors for erectile dysfunction. In fact, erectile problems may be a warning sign of these conditions in men at risk for atherosclerosis. Men who experience ED have a greater risk for angina, heart attack, or stroke.

Erectile dysfunction is a very common problem in men with high blood pressure. More than 40% of men with erectile dysfunction have hypertension. Many of the drugs used to treat hypertension (such as calcium channel blockers and beta-blockers) may also cause ED.

Diabetes

Diabetes is a major risk factor for erectile dysfunction. Between 30 - 50% of all men with diabetes report some form of sexual difficulty. Blocked arteries and nerve damage are both common complications of diabetes. When the blood vessels or nerves of the penis are involved, erectile dysfunction can result. Diabetes is also associated with heart disease and chronic kidney disease, other risk factors for ED.

Obesity

Obesity increases the risk for diabetes, heart disease, and erectile dysfunction.

Metabolic Syndrome

Metabolic syndrome -- a cluster of conditions that includes obesity and abdominal fat, unhealthy cholesterol and triglyceride levels, high blood pressure, and insulin resistance -- is also a risk factor for erectile dysfunction in men older than 50 years.

Benign Prostatic Hyperplasia

Surgery and drug treatments for benign prostatic hyperplasia, such as finasteride (Proscar), can also increase the risk for impotence.

Neurologic Conditions

Diseases that affect the central nervous system can cause erectile dysfunction. These conditions include Parkinson's disease, multiple sclerosis, and stroke.

Endocrinologic and Hormonal Conditions

Low levels of the male hormone testosterone can be a contributing factor to erectile dysfunction in men who have other risk factors. (Low testosterone as the sole cause of erectile dysfunction affects only about 5% of men. In general, low testosterone levels are more likely to reduce sexual desire than to cause impotence.) Abnormalities of the pituitary gland that cause high levels of the hormone prolactin are also associated with erectile dysfunction. Other hormonal and endocrinologic causes of erectile dysfunction include thyroid and adrenal gland problems.

Physical Trauma and Injury

Spinal cord injury and pelvic trauma, such as a pelvic fracture, can cause nerve damage that results in impotence. Other conditions that can injure the spine and effect impotence include spinal cord tumors, spina bifida, and a history of polio.

Surgery

Surgery for Prostate Cancer. Radical prostatectomy can cause loss of sexual function. Nerve-sparing surgical procedures are proving to be helpful in reducing the risk of impotence. (Radiation treatments for prostate cancer also cause erectile dysfunction.)

Surgery for Colon and Rectal Cancers. Surgical and radiation treatments for colorectal cancers can cause impotence in some patients. In general, colostomy does not usually affect sexual function. However, wide rectal surgery can cause short-term or long-term sexual dysfunction.

Fistula Surgery. Surgery to repair anal fistulas can affect the muscles that control the rectum (external anal sphincter muscles), sometimes causing impotence. (Repair of these muscles may restore erectile function.)

Orthopedic Surgery. Erectile dysfunction can sometimes result from orthopedic surgery that affects pelvic nerves.

Note: Vasectomy does NOT cause erectile dysfunction.

Medications

Many medications increase the risk for erectile dysfunction. They include:

• High blood pressure medications, particularly diuretics, beta-blockers, and calcium-channel blockers.
• Heart or cholesterol medications such as digoxin, gemfibrozil, or clofibrate.
• Psychotropic medication used to treat depression and bipolar disorder such as selective serotonin-reuptake inhibitors (SSRIs), tricyclic antidepressants, monoamine oxidase inhibitors, and lithium. Certain types of antipsychotic medication, such as phenothiazines (like compazine) and butyrophenones (like haloperidol), can also cause erectile dysfunction.
• Gastroesophagelal reflux disorder (GERD) medications, used to reduce stomach acid, such as rantidine (Zantac) and cimetidine (Tagamet).
• Hormone drugs such as estrogens, corticosteroids, and 5-alpha reductase inhibitors.
• Chemotherapy drugs such as methotrexate.

Psychological Causes

Anxiety. Anxiety has both emotional and physical consequences that can affect erectile function. It is among the most frequently cited contributors to psychological impotence.

Stress. Even simple stress can affect sexual dysfunction.

Depression. Depression can reduce sexual desire and is associated with erectile dysfunction.

Relationship Problems. Troubles in relationships often have a direct impact on sexual functioning. Partners of men with erectile dysfunction may feel rejected and resentful, particularly if the affected man does not confide his own anxieties or depression. Tension and anger frequently arise between people who are unable to discuss sexual or emotional issues with each other. It can be very difficult for the man to perform sexually when both partners harbor negative feelings.

In-Depth From A.D.A.M. Diagnosis

The doctor typically interviews the patient about many physical and psychological factors and performs a physical exam.

Medical History

The doctor should take a medical and personal history and may ask about the following:

• Past and present medical conditions, surgeries, and medications
• Any history of psychological problems, including stress, anxiety, or depression
• Lifestyle factors such as alcohol, drug, and dietary supplement use

In addition the doctor will ask about the patient's sexual history, which may include:

• When problems with sexual function began
• The frequency, quality, and duration of any erections, and whether they occur at night or in the morning
• The specific circumstances when erectile dysfunction occurs
• Details of technique
• Whether problems exist in the current relationship

If appropriate, the doctor may also interview the sexual partner.

Physical Examination

The doctor will perform a physical exam, including examination of the genital area and a digital rectal examination (the doctor inserts a gloved and lubricated finger into the patient's rectum) to check for prostate abnormalities. It is important to check the blood pressure and to evaluate the circulation by checking pulses in the legs.

Laboratory Tests

Blood tests may be used to measure testosterone levels to determine if there are hormone problems. The doctor may also screen for thyroid and adrenal gland dysfunction. In addition, the doctor may order tests for blood sugar (glucose) levels to check if diabetes is a factor. For more sophisticated tests, the doctor may refer the patient to a urologist. Because erectile dysfunction and atherosclerosis are often linked, it is important to check cholesterol levels.

In-Depth From A.D.A.M. Treatment

Many physical and psychological situations can cause erectile dysfunction, and brief periods of impotence are normal. Every man experiences erectile dysfunction from time to time. Nevertheless, if the problem is persistent, men should seek professional help, particularly since erectile dysfunction is usually treatable and may also be a symptom of an underlying health problem. It is important to treat any medical condition that may be causing erectile dysfunction.

Treatment Choices

Drug therapy with PDE5 inhibitors is the main treatment for erectile dysfunction. Sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) are the three PDE5 inhibitor drugs approved for treatment erectile dysfunction. In general, if a man is a candidate for PDE5 inhibitor therapy and is satisfied with the results, no further treatment is necessary.

PDE5 inhibitors are not safe or effective for all men. Men who cannot or choose not to take the drugs may have other options, including:

• Medications inserted or injected into the penis
• Vacuum devices
• Surgery (limited to rare cases)

Ultimately, how successful the medical treatment is and how well it is accepted depends, in large part, on the man's expectations and how he and his partner both adapt to the procedure.

Psychotherapies. Some form of psychological, behavioral, or sexual therapy may be recommended for certain patients.

Lifestyle Changes. No matter what the treatment, embarking on a healthy lifestyle is the first and critical step for restoring and maintaining erectile function.

In-Depth From A.D.A.M. Lifestyle Changes

Because many cases of erectile dysfunction are due to reduced blood flow from blocked arteries, it is important to maintain the same lifestyle habits as those who face an increased risk for heart disease.

Diet and Exercise

Diet. Everyone should eat a diet rich in fresh fruits and vegetables, whole grains, and fiber and low in saturated fats and sodium. Because erectile dysfunction may be related to circulation problems, diets that benefit the heart are especially important.

Foods that some people claim to have qualities that enhance sexual drive include chilies, chocolate, scallops, oysters, olives, and anchovies. No evidence exists for these claims.

Exercise. A regular exercise program can be helpful.

Alcohol and Smoking. Men who drink alcohol should do so in moderation. Quitting smoking is essential.

Stay Sexually Active

Staying sexually active may help prevent impotence. Frequent erections stimulate blood flow to the penis.

Change or Reduce Medications

If medications are causing impotence, the patient and doctor should discuss alternatives or reduced dosages.

Psychotherapy and Behavioral Therapy

Even if erectile dysfunction is caused by a physical problem, interpersonal, supportive, or behavioral therapy are often helpful for patients and their partners.

Herbs and Supplements

Generally, manufacturers of herbal remedies and dietary supplements do not need FDA approval to sell their products. Just like a drug, herbs and supplements can affect the body's chemistry, and therefore have the potential to produce side effects that may be harmful. There have been a number of reported cases of serious and even lethal side effects from herbal products. Patients should always check with their doctors before using any herbal remedies or dietary supplements.

Aphrodisiacs are substances that are supposed to increase sexual drive, performance, or desire. Many herbs and dietary supplements are marketed as aphrodisiacs. There are several special concerns for people taking alternative remedies for erectile dysfunction.

Yohimbe. Yohimbe is derived from the bark of a West African tree. Side effects include nausea, insomnia, nervousness, and dizziness. Large doses of yohimbe can increase blood pressure and heart rate and may cause kidney failure.

Viramax is a commercial product that contains yohimbine, the active chemical ingredient of yohimbe, and three other herbs: catuaba, muira puama, and maca. It has not been proven to be either effective or safe, and interactions with medications are unknown

Gamma-Butyrolactone (GBL). GBL is found in products marketed for improving sexual function (Verve, Jolt). This substance can convert to a chemical that can cause toxic and life-threatening effects, including seizures and even coma.

Gingko Biloba. Although the risks for gingko biloba appear to be low, there is an increased risk for bleeding at high doses and interaction with vitamin E, anti-clotting medications, and aspirin and other NSAIDs. Large doses can cause convulsions. Commercial gingko preparations have also been reported to contain colchicine, a substance that can be harmful in people with kidney or liver problems.

L-arginine (also called arginine). Arginine may cause gastrointestinal problems. It can also lower blood pressure and change levels of certain chemicals and electrolytes in the body. It may increase the risk for bleeding. Some people have an allergic reaction to it, which in some cases may be severe. It may worsen asthma.

Dehydroepiandrosterone (DHEA). DHEA is a supplement related to certain male and female hormones. Studies show inconclusive results in its treatment for erectile dysfunction. DHEA may interact dangerously with other medications.

Spanish Fly. Spanish fly, or cantharides, which is made from dried beetles, is the most widely-touted aphrodisiac but can be particularly harmful. It irritates the urinary and genital tract and can cause infection, scarring, and burning of the mouth and throat. In some cases, it can be life threatening. No one should try any aphrodisiac without consulting a doctor.

Other Dietary Supplements Marketed for Erectile Dysfunction. There are numerous other products marketed as "all-natural" dietary supplements and promoted as treatments for erectile dysfunction and sexual enhancement. The FDA has not approved any of these products. In recent years, the FDA has banned from the market many of these dietary supplements and warns that they contain the same or similar PDE5 inhibitor prescription drugs used in Viagra, Cialis, and Levitra.

In-Depth From A.D.A.M. Oral Medications (PDE5 Inhibitors)

Three medicines taken by mouth are approved for the treatment of erectile dysfunction:

• Sildenafil (Viagra)
• Vardenafil (Levitra)
• Tadalafil (Cialis)

These drugs all work equally well. All three are known as phosphodiesterase-5 (PDE5) inhibitors. By blocking the PDE-5 enzyme, these drugs help the smooth muscles of the penis to relax and increase blood flow.

PDE5 inhibitors are generally the first choice of treatment for erectile dysfunction.

Candidates for PDE5 Inhibitors

PDE5 inhibitors are a good choice for men at any age who are in good health and who do not have conditions that preclude taking them.

However, PDE5 inhibitors are not suitable for everyone. Men who take nitrate drugs for angina, or certain types of alpha-blockers for high blood pressure and benign prostatic hyperplasia, should not take PDE5 inhibitors. The PDE5 inhibitors are less effective in men with diabetes and in men who have been treated for prostate cancer.

Men with the following conditions should not take PDE5 inhibitors without the recommendation of their doctors and even then should use them with caution:

• Severe heart disease, such as unstable angina, a recent heart attack, or arrhythmias. Men with heart disease may benefit from an exercise test to determine whether resuming sexual activity increases their risk of a heart attack.
• Recent history of stroke
• Hypotension (very low blood pressure)
• Uncontrolled hypertension (high blood pressure)
• Uncontrolled diabetes
• Severe heart failure
• Retinitis pigmentosa. (With this genetic disease, people do not produce phosphodiesterase-5 and do not respond to PDE5 inhibitors.)

Administration and Effect

PDE5 inhibitors work only when the man experiences some sexual arousal. They are generally effective within 15 - 45 minutes. Sildenafil should be taken on an empty stomach; vardenafil and tadalafil may be taken with or without food. The effects of these drugs may last for several hours, and tadalafil may last for up to 36 hours. PDE5 inhibitors should not be used more than once a day.

Success rates increase with the number of attempts, so a man should not be discouraged if the drug does not work at first.

PDE5 inhibitors can also be used in combination with testosterone replacement therapy for men with hypogonadism (low testosterone levels).

Side Effects

Common side effects of PDE inhibitors include flushing, upset stomach, headache, nasal congestion, back pain, and dizziness.

Effects on the Heart. There have been reports of fatal heart attacks in a small percentage of men taking sildenafil (Viagra). Viagra can cause sudden and dangerous drops in blood pressure when the drug is taken with nitrate drugs, such as nitroglycerine, which are used for angina. No one taking nitrates, including amyl nitrate, should take sildenafil or any other PDE5 inhibitors.

Intercourse itself involves an increase in physical exertion and a small risk of heart attack for patients with known heart disease or those at risk.

Visual Effects. About 2.5% of men who take these drugs develop vision problems that include seeing a blue haze, temporary increased brightness, and even temporary vision loss in a few cases. The effect is usually temporary, lasting a few minutes to several hours. Men at risk for eye problems who take PDE5 inhibitors regularly should have frequent eye examinations with an ophthalmologist. Men should also see an eye doctor if visual problems last more than a few hours.

In a few cases, these drugs have been associated with partial vision loss. The vision loss was caused by non-arteritic anterior ischemic optic neuropathy (NAION), a condition that occurs from poor blood flow to optic nerves. However, doctors note that erectile dysfunction is itself linked to the same vascular problems that cause NAION. Patients who suffer from diabetes, high blood pressure, and heart disease are at higher risk for erectile dysfunction as well as other vascular problems such as NAION. Information concerning vision loss has been added to the labels of these drugs, but the risk of blindness appears small. Still, patients who use this medication and experience a sudden loss of vision should immediately stop taking the drug and contact their doctor.

Hearing Loss. A small number of men have experienced sudden hearing loss in one ear, sometimes accompanied by ringing in the ears and dizziness. If you have this symptom, immediately contact your doctor.

Seizures. There have been a few reports of seizures in men taking sildenafil. These are rare occurrences and it is not clear if there is any causal association.

Risk of Priapism. PDE5 inhibitors pose a very low risk for priapism in most men. (Priapism is sustained, painful, and unwanted erection.) Exceptions are young men with normal erectile function.

Interactions with Other Drugs. In addition to serious interactions with nitrates, PDE5 inhibitors may also interact with certain antibiotics, (such as erythromycin), and acid blockers, such as cimetidine (Tagamet). Patients should tell their doctor about any other medications they are taking.

In-Depth From A.D.A.M. Surgery and Devices

Vacuum Erection Devices

Vacuum erection devices, also called vacuum constriction devices, can generally be used by all men with erectile dysfunction. Patients must receive thorough instructions in the proper use of such devices. They typically work as follows:

• The man places the penis inside a plastic cylinder.
• A vacuum is created, which causes blood to flow into the penis, thereby creating an erection.
• Once an erection is achieved, the man places an elastic ring around the base of the penis to retain the erection. The ring should remain in place for no more than 30 minutes.

Lack of spontaneity is this method''s major drawback.

Penile Implants

Penile implants are an option for men who cannot take medication or for who less invasive treatments do not work. In general, they work well in restoring sexual function, and men are usually satisfied with the results.

Two types of surgical implants are used for the treatment of erectile dysfunction:

• A hydraulic implant consists of two cylinders placed within the erection chambers of the penis and a pump. The pump releases a saline solution into the chambers to cause an erection, and removes the solution to deflate the erection.
• A penile prosthesis is composed of two semi-rigid but bendable rods that are placed inside the erection chambers of the penis. The penis can then be manipulated to an erect or non-erect position.

Erectile tissue is permanently damaged when these devices are implanted, and these procedures are irreversible. Although uncommon, mechanical breakdown can occur, or the device can slip or bulge. In addition, a less than optimal quality of erection may result. Infection is a rare, but serious, complication.

Vascular Surgery

In rare cases, penile vascular surgery may be considered as treatment for erectile dysfunction. Two types of operations are available: revascularization (bypass) surgery, and venous ligation. Some insurance carriers consider these procedures experimental and will not pay for them.

According to the American Urologic Association, men who smoke or who have the following conditions are not candidates for penile vascular surgeries:

• Insulin-dependent diabetes
• Widespread atherosclerosis
• Consistently high blood cholesterol levels
• Injured nerves or damaged blood vessels

Revascularization. The revascularization procedure usually involves taking an artery from a leg and then surgically connecting it to the arteries at the back of the penis, bypassing the blockages and restoring blood flow. Penile arterial revascularization is appropriate only for young men (under age 45) who have blood vessel injury at the base of the pain that was caused by events such as blunt trauma or pelvic fracture.

Venous Ligation. Venous ligation is performed when the penis is unable to store a sufficient amount of blood to maintain an erection. This operation ties off or removes veins that are causing an excessive amount of blood to drain from the erection chambers. Long-term success rates for this procedure are less than 50 percent.

In-Depth From A.D.A.M. Injections or Topical Treatments

Treatments Using Alprostadil

Alprostadil is derived from a natural substance, prostaglandin E1, which opens blood vessels. This medicine is an effective treatment for some men. It can be administered by:

• Injection into the erectile tissue of the penis (such as Caverject or Edex)
• A system that administers the drug in pellets placed in the urethra (MUSE system)

Candidates. Alprostadil is not an appropriate choice for men with:

• Severe circulatory or nerve damage
• Bleeding abnormalities or men who are taking medications that thin the blood, such as heparin or warfarin
• Penile implants

Injected Alprostadil. Injected alprostadil (Caverject, Edex) uses a very small needle that the man injects into the erectile tissue of his penis. About 80% of men describe the pain of administering the injection as very mild.

The drug should not be injected more than 3 times a week or more than once within a 24-hour period.

MUSE System. The MUSE system delivers alprostadil through the urethra. It works in the following way:

• The device is a thin plastic tube with a button at the top.
• The man inserts the tube into his urethral opening right after urination. (Urinating or urine leakage right after administration may reduce the amount of medication.)
• He presses the button, which releases a pellet containing alprostadil.
• The man rolls his penis between his hands for 10 - 30 seconds to evenly distribute the drug. To avoid discomfort, the man should keep the penis as straight as possible during administration.
• The man should be upright, (sitting, standing or walking), for about 10 minutes after administration. By that time, he should have achieved an erection that lasts 30 - 60 minutes. (If a man lies on his back too soon after administration, blood flow to the penis may decrease and the erection may be lost.)
• The erection may continue after orgasm.

The MUSE system should not be used more than twice a day and is not appropriate for men with abnormal penis anatomy.

Side Effects of Most Alprostadil Methods. Certain side effects are common to all methods of administration, although they may differ in severity depending on how the drug is given:

• Pain and burning at the application site.
• Scarring of the penis (Peyronie's disease), which is most likely to occur with injections.
• Sudden, low blood pressure. Symptoms include dizziness, lightheadedness, and fainting. If these symptoms occur, the man should lie down immediately with his legs raised.
• Priapism (prolonged erection). Possible with any method, but less chance with the MUSE system than with injections. If priapism occurs, applying ice for 10-minute periods to the inner thigh may help reduce blood flow. Erections that last 4 hours or longer require emergency care.
• Women partners may experience vaginal burning or itching. The drug may have toxic effects if it reaches the fetus in pregnant women, so men should not use alprostadil for intercourse with pregnant women without the use of a condom or other barrier contraceptive device.
• Other side effects include minor bleeding or spotting, redness in the penis, and aching in the testicles, legs, and area around the anus.

Injections Using Papaverine and Phentolamine

Until the introduction of alprostadil, the two drugs used for injection therapy had been papaverine (Pavabid, Cerespan) and phentolamine (Regitine). Adverse reactions are usually minor but include pain, ulcers, and prolonged erections (priapism). These drugs are rarely used now.

Testosterone Replacement Therapy

Testosterone replacement therapy works best for men with ED who have been diagnosed with hypogonadism (low testosterone levels). Men who have ED and normal testosterone levels are not likely to benefit from testosterone therapy. Studies indicate that testosterone therapy can modestly improve erectile function and libido.

Forms of testosterone therapy include:

• Muscle injections using testosterone enanthate (such as Andryl or Delatestryl) or cypionate (Andro-Cyp, Depo-Testosterone, or Virion).
• Skin patch (Testoderm, Testoderm TTS, Androderm). Depending on the brand, patches may be applied daily to the skin of the scrotum or to the abdomen, back, thighs, or upper arm.
• Skin gel (such as Androgel or Testim). The gel is applied only to the shoulders, upper arms, or abdomen, not directly to the penis. It is extremely important that men thoroughly wash their hands with soap and water after applying the gel, and cover the application site with clothing once it dries. Testosterone gel has caused serious side effects (premature development, genital enlargement) in children who have come in contact with it through secondary exposure. Pregnant women must avoid contact with the gel because the testosterone can harm the fetus.
• Oral forms of testosterone are not recommended because of the risk for liver damage when taken for long periods of time.

Side effects may include acne, breast enlargement, headache, and emotional instability. Testosterone therapy may increase the risk for the following serious side effects:

• Rapid growth of prostate tumors in men with existing prostate cancers. (Taking testosterone does not appear to increase the risk for prostate cancer, but doctors remain concerned.)
• Benign prostatic hyperplasia (BPH), enlargement of the prostate gland
• Liver disease and possibly liver cancer
• Worsening of sleep apnea, especially in men who are obese or who have lung conditions